I reported that my amp was a bit noisy. I was wrong. It was the preamp. Im using the Schiit Valhalla 2 as a preamp and the power amps are dead silent. To tell the truth I've never had much luck with PCB based amps being truly quiet.
Am glad that yours turns out to your liking. Did you make the PCB's yourself?
Will second the CCS option. I first used a 220 Ohm 5 watt resistor bypassed by a 100uF 50VDC cap and the sound was good enough but things tightened with the CCS. MY first set of tubes were the EL84M sovteks. One tube kept "running away" and red plating after about two minutes, but I ended up using JJ's and they work great. I can run the amp all day with no issues.
Anyone know why? I'm guessing a bad tube because the voltages check out fine now.
Am glad that yours turns out to your liking. Did you make the PCB's yourself?
Will second the CCS option. I first used a 220 Ohm 5 watt resistor bypassed by a 100uF 50VDC cap and the sound was good enough but things tightened with the CCS. MY first set of tubes were the EL84M sovteks. One tube kept "running away" and red plating after about two minutes, but I ended up using JJ's and they work great. I can run the amp all day with no issues.
Anyone know why? I'm guessing a bad tube because the voltages check out fine now.
So I recently pulled this amp back out after sitting for quite some time and I am absolutely blown away by how good it sounds with LED bias on the input and output tubes. I kind of write it off originally with the CCS I used as it sounded ok but not amazing. I'm not sure if my tastes have changed over the years or I just didn't give this little guy enough time to shine when I first built it.
If you are looking for a simple EL84 PP amplifier to build, I would highly recommend this circuit with the outputs triode strapped and using LED bias.
At this point I'm not sure there is much more I could do to improve the sound, I feel like I somehow got lucky and hit the perfect mix. Has anyone tried LED bias on the cathodyne? Short of upgrading parts or improving the PS, is there really anything more that can be done here?
If you are looking for a simple EL84 PP amplifier to build, I would highly recommend this circuit with the outputs triode strapped and using LED bias.
At this point I'm not sure there is much more I could do to improve the sound, I feel like I somehow got lucky and hit the perfect mix. Has anyone tried LED bias on the cathodyne? Short of upgrading parts or improving the PS, is there really anything more that can be done here?
While the amp I have isn't taken from the Tubecad site, it is a triode strapped EL84 pp with zero NFB.
I have LED bias on my input 6cg7 and my cathodyne 6cg7 (6sn7 nine pin equivalent). These are cap coupled to each other.
In my implementation, I found LED bias on the output tubes gave a crack noise when clipping. I got rid of the led bias and put in user adjustable bias supplies for the output tubes.
I have LED bias on my input 6cg7 and my cathodyne 6cg7 (6sn7 nine pin equivalent). These are cap coupled to each other.
In my implementation, I found LED bias on the output tubes gave a crack noise when clipping. I got rid of the led bias and put in user adjustable bias supplies for the output tubes.
I've built a few of Pete Millett's amps using his boards and all have sounded fantastic, but I have the bug to try a P2P build. I think I'll put this project on the "to build" list. 🙂
Do it!
It's a good springboard design to play with different ideas. Very versatile, sounds great.
It's a good springboard design to play with different ideas. Very versatile, sounds great.
2nd question please
Can I replace the 6n1p with 12 ax7 after changing the heater wiring ?
This will be my first p2p project !
thanks
Can I replace the 6n1p with 12 ax7 after changing the heater wiring ?
This will be my first p2p project !
thanks
Glad this came up, I have newbie question... I know how to elevate a filament with a linear supply, three ways, either re-reference the DC ground; or elevate the CT if the filament xformer has that; or elevate a virtual CT there.
But this is an SMPS would I do it the same way? Just reference the SMPS negative side to a voltage divider across the B+?
In your diagram, the SMPS output is floating. You would use a resistive divider (bypassed to ground)
on the HV supply, with the tap connected to one of the SMPS outputs. Check the mfr data sheet or
email them to see if its output can be elevated by 50VDC. Probably it can.
on the HV supply, with the tap connected to one of the SMPS outputs. Check the mfr data sheet or
email them to see if its output can be elevated by 50VDC. Probably it can.
The plate and cathode resistor values (and LED bias) wouldn't be right for a 12AX7, or even close.
And a 12AX7 doesn't make a good concertina/driver. You could share the first dual tube between
channels, and also share a higher current dual tube for the splitter.
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That was my concern in the back of my mind, but I didn't know why I should have that concern. Thanks, I learn something new here every day.
Hi
I actually never built that circuit as is, I modified it to elevate the heaters +60Vdc above ground.
Important; The power supply is a Class II unit, double insulated and therefore has no ground on the primary (120Vac) side. The DC output is floating (not tied to ground).
I added a switch and a few more components near the LM317 to allow me to choose from pure Class A or Class AB.
It’s a nice sounding amp. with the 6N1P-EV.
BR
Eric